Completely agreed. Even out of a million people, this is probably impossible. I'm quite sure humans couldn't do it. To test humans: Take city of million peop

Completely agreed. Even out of a million people, this is probably impossible. I'm quite sure humans couldn't do it. To test humans: Take city of million people. Take photo of one person. Proceed to ask every person in said city "who is this?" Most likely answer is "no idea", so only consider labeled answers. You will obviously get multiple answers for the same photo due to look-alikes. I suspect the look-alike problem is so great that even the best training optimization could not achieve >= 50% system labeling accuracy for a picture of a single person with no other context. You may be able to achieve 50+% labeling accuracy when you present many photos of the unknown individual to those million people, especially if that individual is pictured with other individuals.